T A B L E F C N T E X T S . 



PART I . 



ESSAY ON CLASSIFICATION. 



CHAPTER I . 



THE FINDAMENTAL RELATIONS OF ANIMALS TO ONE ANOTHER AND TO THE WORLD IN WHICH 

 THEY LIVE, AS THE BASIS UE THE NATURAL SYSTEM OF ANIMALS. 



Snciiox 1. Tlie leading features of a natural zoological 



system are all founded in nature. — There is but one 



system, and that is to be read in nature, and was not 



ilcvi^ied by man. The essential divisions of that system 



■ cannot be arbitrary, p. 3-12. 



SiX'Tio.v 2. Simultaneous existence of the most dirersified 

 types under identical circumstances. — Organized beings 

 of the most dirtercnt structure are everywhere found 

 together, p. 12-16. 



Skction 3. Repetition of identical types under the most 

 dirersified circumstances. — Organized beings with the 

 same structure occur in the most different parts of the 

 world, p. 16, 17. 



Ski TIDX 4. Unity of plan in otherwise highly dicersifed 

 types. — The greatest divei-sity of form and of compli- 

 cation of structure may be found under the same plan 

 of structure, p. 18, I 'J. 



Skction 5. Correspomlcnce in the details of structure in 

 animals otherwise entirely disconnected. — Animals, be- 

 tween which no genetic relaliou can bo traced, may 

 nevertheless exhibit the most astonishing correspond- 

 ence in the details of their structure, p. lU-21. 



Skctiox 6. Various degrees and different kinds of relation- 

 ship among animals. — Animals differ from one another, 

 not oidy in degree ; there are also different kinds of 

 differences, p. 21-23. 



Section 7. Simultaneous existence in the earliest geological 

 periods of all the great types of animals. — The leading 

 types of the animal kingdom have made their appear- 

 ance upon the surface of our globe at the same 

 time, p. 23-25. 



Section 8. The gradation of structure among animals. — 

 There is a gradation among animals, though tlicy do 

 not form one continuous series, p. 26-30. 



Section 9. Range of geographical distribution of animals. 



— The range of distribution of different kinds of ani 

 mals is very unequal. Fauna?, p. 30-36. 



Section 10. Identity of structure of wiilely different types. 



— Animals found within entirely disconnected areas 

 may have the same structure, p. 36—10. 



Section 11. Community of structure among animals living 

 in the same regions. — Animals occupying the same re- 

 gion exhibit sometimes a remarkable similarity of 

 structure, p. -11-43. 



